This is the launch page for finding information about GIS data: what is geographic data and the different types (vector versus raster), what are errors in GIS data, metadata, and where to find GIS data on the Internet.
Introduction to GIS Data
Geodatabases Explored – Vector and Raster Data
Vector and raster data types (including aerial and satellite imagery) are described.
GIS Data: A Look at Accuracy, Precision, and Types of Errors
What is the difference between precision and accuracy? What types of errors are found in GIS data? Learn more about error in GIS data.
GIS Data Formats
What are the common GIS file formats? This article describes shapefiles, GML, CAD based file formats, and imagery formats.
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GIS File Formats
Guides to the various file formats and tools for data format conversions.
Imagery
Digital imagery can greatly add to the visualization of GIS data. In addition satellite imagery can be utilized to derive layers via classification processes such as vegetation, land cover and temperature.
What is a Basemap?
Basemaps are creating by combining geographic data to form the background layer of a map.
Understanding GIS Error
Understanding error in GIS data is an important part of GIS analysis.
Metadata
Metadata, known as “data about the data” is critical documentation about GIS data.
Aerial and Satellite Imagery
Satellite Imagery
Article from 2001 briefly describing satellite imagery and a list of (then) available satellite imagery sources.
Orthophotos
Information about aerial imagery and orthorectification.
GIS Data Creation and Analysis
Methods for Creating Spatial Databases
How is geographic data created? Read here about some of the methodology including heads up digitizing, COGO, and geocoding.
Finding GIS Data Sources on the Internet
The Internet has a wealth of sources of downloadable GIS data. Below is information about GIS data warehouses and other sources of GIS data.
Free GIS Data
Looking for free GIS data? Robin Wilson, a PhD student at the University of Southampton, has a frequently updated list of free GIS datasets that he has found in the course of his research and based on recommendations from other GIS users.
The list is broken down into broader categories covering Physical Geography, Human Geography, and individual countries. Within the Physical Geography category, links are available to free GIS data covering elevation, weather, land cover, hydrology, and natural disasters to name a few. The Human Geography organizes links to data covering administrative boundaries, population, war and crimes, and points of interests. The datasets in both of these categories are at the continental and global level.
GIS data covering smaller geographic extents are linked from the individual country sections.
The list continues to be updated as Wilson finds new resources. Visit: Free GIS Datasets.
Digital Elevation Models datasets
CGIAR
SRTM 90m Digital Elevation Data from the Consortium for Spatial Information
National Elevation Dataset (NED)
USGS NED dataset provides high resolution seamless DEM data for the United States. Download from the National Map Seamless Server.
Polar Ice Sheet DEM
Polar Ice Sheet elevation datasets available from the National Snow and Ice Data Center.
World Data
Free and low-cost sources of data for globally based datasets.
(Article originally published: February 2, 2005)
